Month: February 2016

For development purposes I wanted to install Oracle Database 12c Enterprise Edition to Vagrant box so that I could play with it. It should’ve gone quite straight forwardly but in my case things got complicated although I had Oracle Linux and the pre-requirements fulfilled. Everything went fine until it was time to run the DBCA and create the database.

The DBCA gave “ORA-12547: TNS: lost contact” error which is quite common. Google gave me couple of resources to debug the issue. Oracle DBA Blog explained common issues which cause ORA-12547 and solutions to fix it.

One of the suggested solutions was to check to ensure that the following two files are not 0 bytes:

After this I ran the relink again which worked and also the install of the database worked fine.

cd $ORACLE_HOME/bin
relink all

cd $ORACLE_HOME/bin
relink all

Start the listener:

lsnrctl start LISTENER

lsnrctl start LISTENER

Create the database:

dbca -silent -responseFile $ORACLE_BASE/installation/dbca.rsp

dbca -silent -responseFile $ORACLE_BASE/installation/dbca.rsp

The problems I encountered while installing Oracle Database 12c Enterprise Edition to Oracle Linux 7 although in Vagrant and with Ansible were surprising as you would think that on certified platform it should just work. If I would’ve been using CentOS or Ubuntu it would’ve been totally different issue.

Let’s Encrypt is now in public beta, meaning, you can get valid, trusted SSL certificates for your domains for free. Free SSL certificates for everyone! As Let’s Encrypt is relatively easy to setup, there’s now no reason not to use HTTPS for your sites. The needed steps are described in the documentation and here’s short guide how to setup Let’s Encrypt in CentOS 6.x and automate the SSL certificate renewal.

Let’s Encrypt installation

The Let’s Encrypt Client is a fully-featured, extensible client for the Let’s Encrypt CA that can automate the tasks of obtaining certificates and configuring web servers to use them. The installation is simple but in my case on CentOS 6.x I first needed to update to Python 2.7 as Let’s Encrypt supports Python 2.7+ only.

Setting up Lets encrypt

Install Git if you don’t have it yet.

yum install git

yum install git

If letsencrypt is packaged for your operating system, you can install it from there, and the other solution is to use the letsencrypt-auto wrapper script, which obtains some dependencies from your operating system and puts others in a python virtual environment:

Running the client

You can either just run letsencrypt-auto or letsencrypt, and the client will guide you through the process of obtaining and installing certs interactively or you you can tell it exactly what you want it to do from the command line.

For example obtain a cert for your domain using the Apache plugin to both obtain and install the certs, you could do this:

(The first time you run the command, it will make an account, and ask for an email and agreement to the Let’s Encrypt Subscriber Agreement; you can automate those with –email and –agree-tos)

Although you can use the Apache plugin to obtain and install the certs it didn’t work for me. I got an error: “The apache plugin is not working; there may be problems with your existing configuration.” This seems to be an issue with Apache 2.2 and until it’s fixed you can use the webroot authentication method as explained in documentation.

The webroot plugin works by creating a temporary file for each of your requested domains in ${webroot-path}/.well-known/acme-challenge. Then the Let’s Encrypt validation server makes HTTP requests to validate that the DNS for each requested domain resolves to the server running letsencrypt. Note that to use the webroot plugin, your server must be configured to serve files from hidden directories.

Now your certificate and chain have been saved at Let’s Encrypt configuration directory at “/etc/letsencrypt” and “/etc/letsencrypt/live/“ contains symlinks to the latest certificates. Making regular backups of this folder is ideal.

All we have to do now is set it up in Apache.

Configure Apache to use Let’s Encrypt certs

In Let’s Encrypt configuration directory at “/etc/letsencrypt/live/“ the .pem files are as follows (from the Letsencrypt documentation):

privkey.pem: Private key for the certificate.

This must be kept secret at all times! Never share it with anyone, including Let’s Encrypt developers. You cannot put it into a safe, however – your server still needs to access this file in order for SSL/TLS to work.

This is what Apache needs for SSLCertificateKeyFile

cert.pem: Server certificate only.

This is what Apache needs for SSLCertificateFile.

chain.pem: All certificates that need to be served by the browser excluding server certificate, i.e. root and intermediate certificates only.

This is what Apache needs for SSLCertificateChainFile.

fullchain.pem: All certificates, including server certificate. This is concatenation of chain.pem and cert.pem.

Now that we know which file is which we can configure our VirtualHost to use SSL with our new certs. Change the following lines in your Apache’s virtualhost’s SSL configuration:

Automate updating Let’s Encrypt certs

As you surely noticed Let’s Encrypt CA issues short lived certificates (90 days) and you have to renew the certificates at least once in 3 months. Nice way to force sysadmins to automate the process.

To obtain a new version of the certificate you can simply run Let’s Encrypt again but doing that manually is not feasible. Let’s Encrypt is working hard on automating the renewal process but until that we have to do it by ourselves.